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Native Plant Society of Texas

Swamp Milkweed

Asclepias incarnata

Other common name(s):

Pink Milkweed

Family:

Apocynaceae (Dogbane Family)

Plant Ecoregion Distribution Map

This map uses data from the US EPA. EPA  servers have been offline frequently so maps may not display. We are working on a solution.

Chihuahuan Deserts, Edwards Plateau
Chihuahuan Basins and Playas
Balcones Canyonlands, Edwards Plateau Woodland

Plant Characteristics

Growth Form

Herbaceous, Wetland

Height

2
to
5
ft.

Spread

2
to
5
ft.

Leaf Retention

Deciduous

Lifespan

Perennial

Habitat and Care Requirements

Soil Type(s)

Clay, Moist, Mud, Rich

Light Requirement

Sun, Part Shade

Water Requirement

High

Native Habitat

Grassland, Riparian, Wetland, Woodland

Bloom and Attraction

Bloom Color

Pink, Purple

Bloom Season

Summer, Fall

Seasonal Interest

Larval Host, Nectar, Pollen

Wildlife Benefit

Bees, Butterflies, Hummingbirds

Maintenance

Swamp milkweed is underutilized in gardens. It grows best in shallow water, consistently moist soil, or mud, rather than deep water Good for water gardens or pond edges. Swamp milkweed will inevitably have aphids. The insects are not a problem unless the plant looks sick; at that point an effective treatment is to spray the plant and aphids with soapy water. Set up a pond or a water collection tank near a downspout to supplement water. WARNING: all parts of the plant are poisonous. Native habitat: wet meadow, prairie, riparian, swamp, marsh, margins of flooded plains, lakes, ponds. openings in pine to pine-oak woodlands.

Description

Blooms June-October. Narrow, lance-shaped leaves line the erect, open-branched stem. Small, fragrant, deep pink flowers appear in showy clusters at the end of stems. The fruit is a long narrow pod, filled with tiny brown seeds, attached to hairy tufts. The juice of this species is less milky than that of other milkweeds. Although still listed by some in the Asclepiadaceae Family, the majority of botanical organizations now list it in the Apocynaceae Family. Larval host: Monarch and Queen butterflies.

References

1) Griffith, Bryce, Omernick & Rodgers (2007). Ecoregions of Texas. 2) https://www.wildflower.org/plants/result.php?id_plant=ASIN. 3) https://portal.torcherbaria.org/portal/taxa/index.php?taxon=Asclepias+incarnata&formsubmit=Search+Terms. 4) http://bonap.net/TDC/Image/Map?taxonType=Species&taxonId=1413&locationType=County&mapType=Normal. 5) https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=30241#null, 6) https://seedsource.com/swamp-milkweed/, 7) https://www.wildflower.org/expert/show.php?id=10705#:~:text=They%20say%20that%20milkweeds%20can,so%20timing%20is%20very%20important. 8) https://en.wikipedia.org/wiki/Asclepias_incarnata#:~:text=Asclepias%20incarnata%2C%20the%20swamp%20milkweed,species%20of%20insects%20and%20mammals. 9) https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=g410

Learn about how to propagate Texas native plants.

Material Treatment Method Collection References
Seed No Treatment Plant seeds in a pot outdoors in the fall, winter or early spring. The wet, cold conditions mimic wild seed propagation in nature and the seeds will germinate in mid spring. Germination is poor at temperatures higher than 85 degrees Fahrenheit. Seedlings should not be transplanted until they have at least one set of true leaves. Allow 4 to 8 weeks inside growing time for seedlings before moving to a cold frame or transplanting outside. Plants can be moved outside once the danger of frost has passed. Collect seeds in the fall, when the brown pods are dry and have begun to split. Crack the pods open completely allowing the seeds to dry for one to two weeks in paper bags. Several weevil larvae prey on developing seeds, so look for signs of damage including small entry holes in the pod exuding latex. 1) https://www.nrcs.usda.gov/plantmaterials/wvpmcot12252.pdf 2) https://wildseedproject.net/blog/swamp-milkweed#:~:text=To%20grow%20your%20own%20swamp,will%20germinate%20in%20mid%20spring.
Seed Stratification Place the seeds in a moist medium and store them in a refrigeratore at 35-38 F, for 4-12 weeks. After stratification, sow the seeds just beneath the soil sureface in seedling trays filled with draining seedling mix. Maintain ambient temperatures between 65 and 75 F, and keep the soil consistently moist. Germination typically occurs within a few weeks. Collect seeds in the fall, when the brown pods are dry and have begun to split. Crack the pods open completely allowing the seeds to dry for one to two weeks in paper bags. Several weevil larvae prey on developing seeds, so look for signs of damage including small entry holes in the pod exuding latex. 1) https://www.nrcs.usda.gov/plantmaterials/wvpmcot12252.pdf 2) https://www.gardenia.net/plant/asclepias-incarnata-swamp-milkweed 2) https://www.gardenia.net/plant/asclepias-incarnata-swamp-milkweed
Stem Cutting Dip the cut ends in rooting hormone to encourage root development. Insert the treated cuttings into a moist medium such as sand or potting soil. Keep the medium consistently moist until the stem develops roots. Roots typically develop within 6-10 weeks. after which the plants can be moved to their permanent location. During the summer, choose healthy, green stems approximately 1/3 inch in diameter. Cut the stems under water to prevent air embolism. https://www.gardenia.net/plant/asclepias-incarnata-swamp-milkweed
Root Division While division is possible, it's important to note that Swamp Milkweed has a deep taproot. making it sensitive to disturbance. https://www.gardenia.net/plant/asclepias-incarnata-swamp-milkweed
Seed Scarification Good germination results have been reported without stratification by soaking the seed. Soak the seed in hot water (190 degrees Fahrenheit) for 12 hours. Repeat this process two additional times for expected seed germination of 50%. Seed can be placed in cold storage for up to three years. Germination is poor at temperatures higher than 85 degrees Fahrenheit. Seedlings should not be transplanted until they have at least one set of true leaves. Allow 4 to 8 weeks inside growing time for seedlings before moving to a cold frame or transplanting outside. Plants can be moved outside once the danger of frost has passed. Collect seeds in the fall, when the brown pods are dry and have begun to split. Crack the pods open completely allowing the seeds to dry for one to two weeks in paper bags. Several weevil larvae prey on developing seeds, so look for signs of damage including small entry holes in the pod exuding latex. https://www.westernnativeseed.com/plant%20guides/ascincpg.pdf

About the Region

2026 Fall Symposium Logo

This low-elevations region of Texas extends inland from the barrier islands, about 60 or so miles, and stretches from Brownsville to Louisiana. In total, it covers about 9.5 million acres, with a high point of 150 feet in elevation. More than 1000 species of plants can be found in this region. On the southern end, species more common in Mexico (such as Sabal mexicana) and Central America occur.

The barrier islands provide us with dune systems, and clay flats to the inland side, which have species found in these areas alone. Many plants here, such as Ipomoea pes-caprae (beach morning glory), can be found throughout tropical regions of the globe. I’ve encountered the same species on the beaches of Guam.

Once inland, vast marshes and wet prairies occur. Occasionally, oak (Quercus fusiformis) groves can be found. Common grasses include species of Bothriochloa, Paspalum, and Sporobolus; eastern gamagrass (Tripsacum dactyloides); and switchgrass (Panicum species). Many rivers and creeks cut through the Gulf Prairies, and along these riparian areas various species of trees, Sabal minor, and other plants adapted to clay soils can be found. Due to overgrazing, farming, and fire suppression, woody species such as mesquite (Prosopis glandulosa) and huisache (Acacia farnesiana), and invasive species such as chinaberry (Melia azedarach), Brazilian pepper (Schinus terebinthifolius), and Chinese tallow (Sapium sebiferum) have increased and displaced our native flora.

Source: Wildflowers of Texas by Michael Eason